Many processes and applications rely heavily on the use of liquids. Liquids are typically stored in tanks, such as reserving tanks, and are transported from such reserving tanks to process stations where they are required by way of piping lines.
It is desirable in any storage, transportation or process use of fluids to be aware of any tank or plumbing fluid leaks or breaches. Even minimal fluid leaks can be detrimental, not only from a material loss standpoint, but also from the standpoint of environmental and safety considerations if such fluids happen to be hazardous materials.
A variety of fluid leak detection schemes are known. For example, so-called differential pressure techniques may be used to detect the existence of leaks in a tank or piping. However, such techniques generally fail to identify localization of a leak and may have difficulty if not total inability to detect the existence of very small leaks. Furthermore, such techniques may experience significant time lag between when a leak first occurs and when the leak is detected rendering such detection techniques undesirable in time critical leak detection applications.
Piping and tank leaks may also be detected by way of discrete, uninsulated electrode pair placements wherein a fluid leak that causes the fluid to bridge the electrodes is detected as a short across the electrodes or as a significant change in the resistance between the electrodes. The fact that such a technique uses exposed or uninsulated electrodes may be problematic in applications using flammable fluids as they represent a potential ignition source.
Certain other techniques have been proposed which utilize a coaxial conductor cable wherein the dielectric layer that is intermediate the solid central and braded exterior conductors is porous. Infiltration of the fluid from a leak to be detected into the porous intermediate layer causes a substantial change in the permitivity of the layer at the infiltrated location. Pulse reflection distortion techniques are then utilized to detect the presence and location of the leak. This proves to be a solution requiring expensive and sophisticated electronics for generating and interpreting signals. Furthermore, it is recognized that such techniques may be slow to detect leaks due to wicking effects of the braided outer layer which slows the infiltration of the leaked fluid through the porous intermediate layer and may distribute the liquid over a exceptionally long length of the cable.
Yet another option in fluid leak detection is disclosed in commonly assigned and co-pending U.S. patent application Ser. No. 09/881,389, Attorney Docket No. 67,200-438. In that application, a thermal sensing fluid leak detection scheme is described. Temperature changes in the detector due to fluid contact are detected in such a scheme. While the invention described therein is regarded as an improvement over the prior art, it may not meet all requirements of certain fluid leak detection applications. For example, a plurality of such individual thermal leak detection apparatus may be required to adequately canvas an area of interest for the purpose of leak detection. Even then, the granularity of localizing the source of such leaks may be greater than that desired in a particular application.